According to the National Cancer Institute, breast cancer is second only to lung cancer in causing the deaths of American women. An estimated one in eight women (12.6%) will develop breast cancer in their lifetime. More than 180,000 women per year are now diagnosed, often too late for lifesaving treatment. Highly sensitive and specific detection is critical to early diagnoses and successful treatments for most breast cancers. MRI has great potential as a tool for imaging and spectroscopic detection of breast cancer in women, especially for those under 50 years of age. Younger women frequently have "radiodense' breast tissue, rendering breast cancer diagnosis with conventional mammography problematic. For this reason and others, contrast-enhanced MRI of the breast has emerged as one of the most promising clinical tools for detection of breast cancer and delineation of its anatomic extent. NMR spectroscopy in vivo of cellular metabolism in tumors may further augment imaging diagnostic methods. To encourage the promise of magnetic resonance based diagnostics, the NCI has issued at least a dozen program annDuncements over the past decade specifically requesting grant applications for MR based investigation of breast cancer. Based on preliminary human breast exams performed at 4T, and on additional human imaging experience at 4T and 7T, we postulate that the most sensitive and highly specific detection of breast cancer by MR imaging and spectroscopy methods will require the use of high sensitivity breast coil receivers together with high homogeneity chest coil transmitters, at the highest magnetic fields available. We intend to investigate this hypothetical assertion by developing a single tuned and multinuclear chest coils paired with phased array receivers to make dual breast imaging and spectroscopy possible at 4T and 7T. Currently there are no such capabilities for high field breast studies. Cancer detection in breasts will be improved with this new high field technology by the increased signal-to-noise, spectral resolution and fat suppression it facilitates. Specificity will be improved and scan time reduced by imaging both breasts simultaneously to facilitate anatomic and metabolic comparison between healthy and cancerous breasts for an individual. The chest coils will be actively switched between transmit and receive modes, and will be actively decoupled from the independent breast receiver coils. This new RF technology will be tested on forty breast cancer patients by the breast imaging and spectroscopy methods proposed. Improvements in data quality and diagnostics results will be evaluated toprove the new technology and methods developed.